Invasive Stink Bugs and Related Species (Pentatomoidea)

688 Invasive Stink Bugs and Related Species (Pentatomoidea)

allylpropargyl alcohols to bicyclo[3.1.1]hexanes (Fürstner and Schlecker 2008). Thus, the reaction of chi-
ral allylzinc 32 , generated in several steps from (R)-citronellal, with 3-trimethylsilylpropynal ( 33 ) in the
presence of a chiral, deprotonated bisoxazoline ligand under Nakamura reaction conditions (Nakamura
et al. 1998) at -100oC was appreciably enantioselective and afforded (3S)-enynol 34 (R = Me 3 Si) with
~ 10:1 dr. At the more convenient -78oC, the reaction gave a somewhat lower 8.8:1 diastereomeric ratio
and without the chiral ligand, it was completely non-diastereoselective. After removal of the Me 3 Si pro-
tecting group, propargylic alcohol 35 was converted to the p-nitrobenzoate 36 followed by AuCl 3 ( P y)-
catalyzed cycloisomerization to produce ketone 20 (dr 19:1) after hydrolysis of the initially formed enol
ester (Fürstner and Schlecker 2008). Cleavage of ketone 20 with ozone gave aldehyde 21 , which was
converted to 10 in three steps as described previously (Figure 15.3). Availability of multiple synthetic
procedures for this unique sesquiterpene stink bug pheromone with a bicyclo[3.1.1]hexane skeleton may
afford sufficient material to fully assess its biological activity. The biological activity has been studied
with the natural pheromone isolated from E. lewisi (Takita et al. 2008), and diastereomeric mixtures
(Mori 2007), and with synthetic stereoisomer 10, showing that it attracted significantly more bugs than
the diastereomer with (2Z,6R,1′R,5′R) configuration, which appeared inactive. Furthermore, synthetic 10
was as attractive as natural extract or live males. Intriguingly, neither synthetic 10 nor natural extracts
attracted any males in field tests. Furthermore, isomers with the (2Z,6S) configuration appeared neither
to inhibit nor enhance attraction to 10 (Mori et al. 2008).

15.2.9 Halyomorpha halys (Stål) [Pentatomidae: Pentatominae: Cappaeini]

The brown marmorated stink bug, Halyomorpha halys, first identified in the United States in
Pennsylvania  in 2001 (Hoebeke and Carter 2003), has now been found in 41 states and Canada. It

CHO a

ZnBr OHC SiMe^333

CHO X

OH

R

f

O O

O

OC 6 H 4 NO 2

OH

R

CHO

30 : X = OH

34 : R = Me 3 Si, dr 10.4:1

35 : R = H

31 : X = Br

bd

c

g

e

hi

j

(R)-citronellal 11

32

36 20

10

21

FIGURE 15.6 Stereocontrolled synthesis of Eysarcoris lewisi pheromone 10 through asymmetric addition of allylzinc
32 to acetylenic aldehyde 33 and gold-catalyzed cycloisomerization of chiral enynol 36. a) CH 2 O, EtCO 2 H/Py; b) NaBH 4 /
CeCl 3 ; c) Br 2 /Ph 3 P; d) Zn; e) 2,2’-methylene-bis-[(4S)-4-phenyl-2-oxazoline]; f) K 2 CO 3 /MeOH; g) p-NO 2 C 6 H 4 COCl/Py/
DMAP; h) 1. AuCl 3 /Py, 2. LiOH; i) O 3 ; j) Tashiro and Mori (2008).